The present invention relates to aerial scanning of the ground to detect movement of objects on the ground. In the past, radar has been used for scanning the ground from the air to detect moving targets. Radar is an active system; that is, it employs transmitted and received signals in its operation. However, passive systems which do not use transmitted signals are preferred because they are less vulnerable to detection and jamming. Although infrared sensing has been employed in detection systems, no efficient passive system is known which is computerized and can automatically identify moving objects with optimum efficiency.